The present invention is related to a top vacuum corrugated feeder (TVCF) and more particularly to a TVCF having air parameters which are self adjusting based on characteristics of sheets in the supply tray.
With the advent of high speed photocopying machines, a document (i.e., sheet) handler to feed sheets to the copy platen of the copier and a copy sheet feeder to feed copy sheets to a transfer station in a rapid dependable manner are needed to realize the full potential copy output of the copier. A number of currently available document handlers and sheet feeders provide such rapid transfer. However, these document handlers and copy sheet feeders are often accompanied by a certain risk of mis-feeds and multi-feeds while maintaining high handling speed. The greatest number of problems occur during the initial separation of the sheet sought to be acquired from the stack of sheets.
To provide a delicate yet positive feed, conventional copying machines employ a vacuum feed belt assembly beneath the stack of copy sheets to be fed for acquiring the bottom sheet in the stack by vacuum, and driving belts to move the acquired sheet from under the stack into the path of sheet movement (see e.g., FIG. 5). To prevent mis-feeds and multi-feeds, an air knife is positioned near the lead edge of the stack for injecting air providing an air bearing between the acquired sheet and the stack. This air bearing greatly reduces the force necessary to pull the bottom sheet from the stack and also minimizes the possibility of the adjacent sheet being pulled out from under the stack with the sheet being fed.
When using the document handler or sheet feeder with a large variation in the size of the document stack placed therein is desired, providing the correct air flow from the air knife may be difficult. For example, with a very small stack of documents, excessive air flow could cause excessive document flutter or, in the extreme, actually blow documents out of the document tray or blow sheets out of the sheet holder. On the other hand, with a large stack of documents the air flow might be insufficient to produce the required separation between the sheets which would result in the increased likelihood of mis-feeds or multi-feeds. Some devices adjust the quantity of air from the air knife based on the weight or pressure of the sheets in the sheet feeder (see e.g., U.S. Pat. No. 4,566,683, incorporated herein by reference) or based on the friction between the bottom two sheets of a stack (see e.g., U.S. Pat. No. 4,638,986, incorporated herein by reference). However, these devices only adjust the air knife and only base that adjustment on characteristics of the stack itself, or the characteristics of sheets with respect to the stack. Further, these adjustments are more suitable for bottom vacuum corrugated feeders than for top vacuum corrugated feeders (TVCFs).
The aforementioned devices fail to further reduce mis-feeds and multi-feeds due to differences in paper size and paper basis weight. In addition, the aforementioned devices only consider one air parameter, i.e., the air knife. In other words, if air parameters are optimized for a paper having a particular basis weight and size, the copier will not perform as well when paper having a different basis weight and/or size is used. Such a copier lacks the flexibility desired by discriminating users. Although air parameters may be chosen that will permit a range of different paper basis weights and paper sizes, these parameters will not afford optimal operation of the sheet feed system. Therefore, while the aforementioned devices may reduce mis-feeds and multi-feeds based on characteristics of the supply stack, they do not optimize performance by adjusting air parameters to accommodate different paper characteristics.